gtk2: make gtk2 look for immodule cache in $NIX_PROFILE

pkgs/development/libraries/gtk+/2.0-immodules.cache.patch

@@ -0,0 +1,27 @@
+--- a/gtk/gtkrc.c	2014-09-30 05:02:17.000000000 +0900
++++ b/gtk/gtkrc.c	2016-04-09 17:39:51.363288355 +0900
+@@ -445,5 +445,23 @@
+   if (var)
+     result = g_strdup (var);
+ 
++  // check NIX_PROFILES paths.
++  const gchar *nixProfilesEnv = g_getenv ("NIX_PROFILES");
++  gchar *cachePath;
++  guint i;
++
++  if(nixProfilesEnv && !result){
++    gchar **paths = g_strsplit(nixProfilesEnv, " ", -1);
++    for (i = 0; paths[i] != NULL; i++){
++      cachePath = g_build_filename(paths[i], "etc", "gtk-2.0", "immodules.cache", NULL);
++      if( g_file_test( cachePath, G_FILE_TEST_EXISTS) ){
++        if(result) g_free(result);
++        result = g_strdup(cachePath);
++      }
++      g_free(cachePath);
++    }
++    g_strfreev(paths);
++  }
++
+   if (!result)
+     {
+

pkgs/development/libraries/gtk+/2.x.nix

@@ -26,6 +26,8 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ setupHook perl pkgconfig gettext ];
 
+  patches = [ ./2.0-immodules.cache.patch ];
+
   propagatedBuildInputs = with xorg; with stdenv.lib;
     [ glib cairo pango gdk_pixbuf atk ]
     ++ optionals (stdenv.isLinux || stdenv.isDarwin) [